Rahmat: Rahman and Rahim both point to one and the same essence of the divine attribute, Rahmat meaning Mercy or Grace. But these are two very different aspects or outcomes of Divine Mercy. Mercy unreserved, shown to one and all of His creatures, be they obedient or disobedient to their Lord, is known as Rahmaaniat. And mercy done specially to those faithful to their lord, as a reward or in appreciation of the goodness of the souls, is called Rahmat.
The attribute Rahmat stands as the source responsible for all His activities i.e. His creation, sustaining, guidance and legislation. Grace means to give willingly without any expectation of returns. No being is out of his Grace. Rahmat signifies All Enveloping, All Penetrating Universal Grace of Allah.
But to give more than what one deserves would mean to waste the grace and spoil the individual. Everyone of His creatures should not and does not receive His Grace less, or more than its individual merit or capacity. As he gives each according to its merit and reception, his gift is Adl, and this is Grace restricted by merit as implied in the word Rahmat.
Both Rahman and Rahim represent the fact that Grace and Justice in divine activity are not two separate attributes which can be conceived one without the other. Every being, in its state of existence, represents His Grace as well as His Justice.
Rab (in Rabbul-Aalameen): By 'Rab' is meant The One who gives everything its shape and guides it to reach it.
"A'ta kulla shaiyin khalaqahu thumma hada'According to Raghib, an Arab lexicologist, the word Rab signifies 'the fostering of a thing in such a manner as to make it attain one condition after another until it reaches its goal of completion.'
He is the one who gave everything its shape and guided it to reach it.
Allah is Rabbul-Aalameen. He is the Lord, Cherisher, Nourisher and Sustainer of everything, the earth and the heavens, the known and the unknown, the seen and the unseen, the dry and the wet, the animate or inanimate, the visible and the invisible, the perceptible and imperceptible, the Rab of All Universes.
And by the word Rab it is signified that He is not only the Creator, but also Sustainer, Nourisher, Cherisher, stage by stage till completion of shape. The role of Rab starts as early as the will to create a being and when the being is created, to nurture it with love, devotion, never ceasing vigilance and care, providing with everything the creature needs according to the changes it is evolved through. Such is the Rububiyat of the Lord of the Worlds.
Again, the name Rabbul-Aalameen for Allah implies His Adl, or Justice. Man is warned of any kind of injustice to anyone in the creation of God, for God being the All Merciful Lord who has nourished and cherished a being, if even in the least be hurt, will not be pleased, and will not leave the offender, unpunished. This punishment is the very outcome of his Benevolence and Mercy. It is just like a mother who punishes one child for hurting the other, though she loves them both equally.
Haamid (the praiser) and the Mahmood (the praised one): Alhamdu means all praise, thanks, gratitude, indebtness and obligation in the real meaning and in every sense of the word, from the time when even time wasn't created to eternity, is due to none else but Allah and Allah alone, not by any force or compulsion but because only He deserves it.
If a man praises his Lord, Allah, then the question arises as to who is praising whom? The created is praising the Creator. How is this possible? How can the creation praise the Creator? It is only possible when the Creator has guided and taught the Created to praise! In fact, it is none else than Allah who is Haamid (i.e. The Praiser) and Mahmood (i.e. The Praised One). There is none else besides Him as He is the subject as well as the object of the praise. This quality can not be shared except Allah, who alone possesses these names.